Desulfurization in the gasification of coal



Patented Oct. 12, 1954 DESULEURIZATIDN IN THE GASIFICATION OF COA'IJ Bertrand Ji -M'ayland;- Bartlesvillq: 0kla.,. assignorr to Phillipstlietroleum Company, a corporation ofiDelaware:

AppficationD'eccmb'er 15, 1950, Serial No. 200,984

'tClaims:v 1

This invention relates toan' improvedprocess for the removal of sulfur simultaneously with the gasification of carbonaceous e materials;

The sulfur content of 'coals 'maybe as-high as 10 per cent by weight or more andfdrthismeason fuel gas or synthesis gas' made-by conventional coahgasifibation 'processesis; in many cases; high in sulfur, which isundesirable for various-reasons such ascorrosion; catalyst poisoning; gum formation, etc. Sulfur compounds may be re moved from the gasbyi many methods" including physical absorptionand chemical reaction" but because of the volume" of the gas *streamand-the presence of high carbon dioxide: content; these methods are expensive.

The present" invention provides a" method "for the removal of sulfur simultaneously with" the gasifikiation of a carbonaceous material thus eliminating costly' purification steps: According tothe present invention; iron-onanoth'er metal carbonyl, formed'from finely divided-iron and a portion of the carbon monoxide containing gas from the'gasification step; is condensed anda'b sorbed' on the surface ofthe coal particles; The carbonyl treated coal particles" are then'- fed to a gasification-chamber: At the temperature of gasificationthe carbonyl is" decomposed"to'- ele'e mental iron which is finely dispersed through outtheproducts of initial gasificationandis free to react with sulfur compounds. Iromsulfid'e-is formed and is takenofi with the ash, and agasification'productwith alowered'sulfur content is produced.

In.-.order to have the ironiwidely dispersed-isothat excessive amounts will notice requiredzithe following'procedure is preferred. Finelyydivided iron-fromany source such as forexampleva; used fluidized iron synthesis catalyst, is contacted with carbon monoxide containing gas from the gasification step at the most favorable conditions of temperature and pressure for carbonyl formation and volatilization. These conditions are given in the published literature. See, for example, Researches on the Metallic C'arbonyls, R. L. Mond and A. E. Wallis, Journal Chem. Soc., 121, 29-32 (1922). According to this reference, favorable conditions ofiron carbonyl formations are:

2-. inc-possession of this.disclosureathat:metalsxother thanzironzmay: beus'ectl in vth-isr processv Theegas containing: the; hunt-carbonyl; vaportis :zthen"; con; tactedirwithtpowdered coaliin thecoalafeedtchamr-v ber of a: gasification plants. Withisomencoo-ling the-"irorrtcarbonyl isaboth condnsedrand: absorbed on:ther-:.surface.:offthe coal particles: Uponaene tering .the gasificationr chambert'the: carbonyl. is decomposeditotelemental ironiwhich'is :then free torreact withcsulfurrcompoundsr In therdrawing thererisdiagrammatically rep resented-r. one form. of: apparatuswhich .may'i' be used." tot-practice? that process: of my invention; Thetprocessrsis'edescrihedvwitli respect:to coaltbut ittcamhereadily modifiedtior any-carbonaceous material i-suchi as::- ground? oil shale; shale: oi'L. res finery-rresiduum; etc. Inzpreparing the coal or other: carbonaceous materiallfor gasification;..it isa-desirable2 to: pnlverize .it toarelativelyfiherstate of.:.subd-ivision-,". preferably suchi that: it WilliDEiSS I the: coal: is: conducted; through: feed? line 10K to chamber H. In chamheri'll;.the'rpowderedrcoai is zcontact'edzwith :ironucarbonyl vapor containing gassfrom line::l2. z This =.gas issa 'recyclegas from the-s gasifi-cation; process, containswcarbon: mon= oxid'e andfis contacted-.twith-faifinely Jdividedsiiron in chamber l3.atsuitable conditions tot form'iiiron' carbonyli. Thepowdered coal. being at 'roonr temperature; the iron: carbonyl: is: both condensed and. absorbed ion the surfacestof the coal particles in chamber H: The powdered: coal .is withdrawn from chamberrlrl througl'i-iilines. l t ite a separation zone: l5. Gasesfare removed: fromizthefseparation zone *l'stthroughiline-F [6. The powd'eredzcoal is withdrawn from the separation zone l5 through line I! and blown into the gasification chamber I8 together with oxygen from line I!) and/or steam from line 25. Upon entering the gasification chamber [8, the carbonyl is decomposed to elemental iron which is finely dispersed throughout the product of initial combustion and is free to react with sulfur compounds. Typical operating conditions for the first gasification stage are:

Preferred Broad Range Range Temperature, F 1,400 to 3,000.... 1,800 to 2,500. Pressure, Atms 1.5 to 30 2 to 15. Contact time, Seconds 0.1 to 10 l to 5 It will be apparent to one skilled in the art A lower temperature will give a lower hydrogen sulfide concentration and would be desirable for fuel gas since methanation would occur and be catalyzed by the iron. Typical operating conditions for the second gasification stage are:

The lower temperature in the second stage gasification may be obtained by a water or steam quench 29, or by any cooling method known to the art.

The thermodynamic equilibrium for the system Fe-FeS--H2H2S is such that at 1600" F., H2S/I-I2=300 With a concentration of hydrogen at 40 per cent, hydrogen sulfide is 0.13 per cent; thus most of the sulfur leaves as iron sulfide in the ash from the coal. A lower temperature results in an even lower hydrogen sulfide concentration and would be desirable for fuel gas since methanation, which is the formation of methane, would occur and be catalyzed by the iron. For synthesis gas the high temperature is desirable to reduce the residual hydrocarbon, though sulfur removal is less complete and a further sulfur removal step may be desirable.

The gasification products are withdrawn through line 20 to a separation zone 2! Where the ash and iron sulfide are taken off through line 22. The gasification products are withdrawn through line 23 and passed to cooling and purification zones 26. Any cooling method and any scrubbing oil known to the art may be used. Tar oil and sludge are removed through line 2'! and water removed through line 24. The fuel gas is removed through line 28. A part of the fuel gas containing carbon monoxide is recycled through line 3| to the iron chamber 13, where iron carbonyl is formed from contacting iron with the carbon monoxide containing gas. This gas and iron carbonyl contained therein are then withdrawn through line l2 to contact the coal in zone H as previously described.

Herein and in the claims it is to be understood that coal has as its full equivalent other gasifiable carbonaceous materials, the essence of the present invention being substantially as set forth in the following paragraph.

Reasonable variation and some modification are possible within the scope of the foregoing disclosure, drawing, and the appended claims to the invention, the essence of which is that in situ formation of an elemental metal, e. g. iron, from a metal carbonyl, is used in a gasification process to simultaneously desulfurize the gases being pro- 4 duced and that a method for so doing has been set forth.

I claim:

1. A process for the gasification of a solid powdered carbonaceous material containing sulfur which comprises introducing said material and a metal carbonyl into a gasification zone, subjecting said mixture to gasification conditions with the introduction of an oxygen-supplying gas so as to supply the heat of reaction and react the metal of the metal carbonyl with the sulfur component of the carbonaceous material to produce the metal sulfide, removing the metal sulfide from the gases produced and recovering said gases.

2. A process according to claim 1 in which the gasification is carried out in two gasification stages and in which there is effected a cooling of the gases intermediate said stages so as to reduce the temperature of the gases entering into said second stage to a level at which methanation is effected.

3. A process according to claim 1 wherein the solid carbonaceous material is coal and the carbonyl is iron carbonyl.

4. A process according to claim 1 wherein the gasification is effected at a temperature in the range 1400-3000 F. under a pressure of 1.5-30 atmospheres and the time is of the order of 0.1-10 seconds.

5. A process for the gasification of a solid carbonaceous material containing sulfur, which comprises subdividing said material to form a powder thereof; admixing with said powder a metal carbonyl; then introducing said powder admixed with said metal carbonyl into a gasification zone, gasifying said powder at a gasification temperature; then separating gases thus produced from solid residue of the carbonaceous material and metal sulfide formed and recovering said gases.

6. A process according to claim 5 wherein a portion of the gases formed are contacted with a metal to form additional metal carbonyl.

7. A process according to claim 5 in which the gasification is carried out in two gasification stages and in which there is effected a cooling of the gases intermediate said stages so as to reduce the temperature of the gases entering into said second stage to a level at which methanation is efiected.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 676,245 Strache June 11, 1901 809,087 Blackmore Jan. 2, 1906 2,221,061 Simpson Nov. 12, 1940 

1. A PROCESS FOR THE GASIFICATION OF A SOLID POWDERED CARBONACEOUS MATERIAL CONTAINING SULFUR WHICH COMPRISES INTRODUCING SAID MATERIAL AND A METAL CARBONYL INTO A GASIFICATION ZONE, SUBJECTING SAID MIXTURE TO GASIFICATION CONDITIONS WITH THE INTRODUCTION OF AN OXYGEN-SUPPLYING GAS SO AS TO SUPPLY THE HEAT OF REACTION AND REACT THE METAL OF THE METAL CARBONYL WITH THE SULFUR COMPONENT OF THE CARBONACEOUS MATERIAL TO PRODUCE THE METAL SULFIDE, REMOVING THE METAL SULFIDE FROM THE GASES PRODUCED AND RECOVERING SAID GASES. 